MEKK-3 Acts Cooperatively with NSY-1 in SKN-1-Dependent Manner against Oxidative Stress and Aging in Caenorhabditis elegans

SIMPLE SUMMARY: Oxidative stress has been linked to myriad pathologies and aging. Here, we show that MEKK-3- and NSY-1-mediated nuclear translocation of SKN-1 is critical for protection against oxidative stress and for longevity in Caenorhabditis elegans. A genetic approach revealed that the knockdown of MEKK-3 and NSY-1, components of the p38 MAPK pathway, significantly reduced the resistance to oxidative stress achieved by SKN-1 overexpression. Mechanistic analyses showed that MEKK-3 and NSY-1 participate in the accumulation of SKN-1 in intestinal nuclei, which is required for the activation of phase II detoxification genes. These results provide molecular insights into oxidative stress resistance and reveal potential targets for aging-associated diseases. ABSTRACT: Oxidative stress resulting from reactive oxygen species and other toxic metabolites is involved in human diseases, and it plays an important role in aging. In Caenorhabditis elegans, SKN-1 is required for protection against oxidative stress and aging. As p38 mitogen-activated protein kinase signaling is activated in response to oxidative stress, SKN-1 accumulates in intestinal nuclei and induces phase II detoxification genes. However, NSY-1, a well-known mitogen-activated protein kinase kinase kinase (MAPKKK) of C. elegans, acts as a partial regulator of the SKN-1-induced oxidative stress signaling pathway, suggesting that the regulator for optimal activation of SKN-1 remains unknown. Here, we report a MAPKKK, MEKK-3, as a new regulator required for full activation of SKN-1-mediated resistance against oxidative stress and aging. In RNA-interference-based screening, we found that the simultaneous knockdown of mekk-3 and nsy-1 significantly decreased the oxidative stress resistance and survival of SKN-1 transgenic worms. MEKK-3 was induced in response to oxidative stress. Mechanistic analysis revealed that double knockdown of mekk-3 and nsy-1 completely suppressed the nuclear localization of SKN-1. These results were reproduced in mutant worms in which SKN-1 is constitutively localized to intestinal nuclei. In addition, mekk-3 and nsy-1 were required for optimal induction of SKN-1 target genes such as gcs-1 and trx-1. These data indicate that MEKK-3 plays an essential role in the SKN-1-dependent signaling pathway involved in oxidative stress resistance and longevity by cooperating with NSY-1.